import pygame
from pygame.sprite import Sprite

class Ship(Sprite):
    
    def __init__(self, ai_settings,screen):
        """ 初始化飞船并设置其初始化位置 """
        super(Ship,self).__init__()

        self.screen = screen
        # 获取游戏设置
        self.ai_settings = ai_settings
        # 初始化向右移动标志
        self.moving_right = False
        # 初始化向左移动标志
        self.moving_left = False      
        # 加载飞船图像并获取其外接矩形
        self.image = pygame.image.load('images/ship.bmp')
        self.rect = self.image.get_rect()
        self.screen_rect = screen.get_rect()      
        # 将每一艘新飞船放在屏幕底部中央
        self.rect.centerx = self.screen_rect.centerx
        self.rect.bottom = self.screen_rect.bottom
        # 初始化飞船位置信息
        self.center = float(self.rect.centerx)

    def blitme(self):
        """ 在指定位置绘制飞船 """
        self.screen.blit(self.image,self.rect)

    def center_ship(self):
        self.center = float(self.screen_rect.centerx)
        #self.rect.centerx = self.screen_rect.centerx
        #self.rect.bottom = self.screen_rect.bottom

    def update(self):
        """ 根据移动标志更新飞船位置 """
        if self.moving_right and self.center < self.screen_rect.right:
            self.center += self.ai_settings.ship_speed
        if self.moving_left and self.center > 0:
            self.center -= self.ai_settings.ship_speed

        self.rect.centerx = self.center